propagate at least the first w3c tracestate header

api/trace/testtrace/trace_context_propagator_test.go

@@ -288,9 +288,26 @@ func TestInjectTraceContextToHTTPReq(t *testing.T) {
 
 func TestTraceContextPropagator_GetAllKeys(t *testing.T) {
 	var propagator trace.TraceContext
-	want := []string{"traceparent"}
+	want := []string{"traceparent", "tracestate"}
 	got := propagator.GetAllKeys()
 	if diff := cmp.Diff(got, want); diff != "" {
 		t.Errorf("GetAllKeys: -got +want %s", diff)
 	}
 }
+
+func TestTraceStatePropagation(t *testing.T) {
+	props := propagation.New(propagation.WithInjectors(trace.TraceContext{}), propagation.WithExtractors(trace.TraceContext{}))
+	want := "opaquevalue"
+	headerName := "tracestate"
+
+	inReq, _ := http.NewRequest(http.MethodGet, "http://example.com", nil)
+	inReq.Header.Add(headerName, want)
+	ctx := propagation.ExtractHTTP(context.Background(), props, inReq.Header)
+
+	outReq, _ := http.NewRequest(http.MethodGet, "http://www.example.com", nil)
+	propagation.InjectHTTP(ctx, props, outReq.Header)
+
+	if diff := cmp.Diff(outReq.Header.Get(headerName), want); diff != "" {
+		t.Errorf("Propagate tracestate: -got +want %s", diff)
+	}
+}

api/trace/trace_context_propagator.go

@@ -19,7 +19,6 @@ import (
 	"encoding/hex"
 	"fmt"
 	"regexp"
-	"strings"
 
 	"go.opentelemetry.io/otel/api/core"
 	"go.opentelemetry.io/otel/api/propagation"
@@ -29,6 +28,13 @@ const (
 	supportedVersion  = 0
 	maxVersion        = 254
 	traceparentHeader = "traceparent"
+	tracestateHeader  = "tracestate"
+)
+
+type traceContextPropagatorKeyType uint
+
+const (
+	tracestateKey traceContextPropagatorKeyType = 0
 )
 
 // TraceContext propagates SpanContext in W3C TraceContext format.
@@ -36,7 +42,7 @@ const (
 type TraceContext struct{}
 
 var _ propagation.HTTPPropagator = TraceContext{}
-var traceCtxRegExp = regexp.MustCompile("^[0-9a-f]{2}-[a-f0-9]{32}-[a-f0-9]{16}-[a-f0-9]{2}-?")
+var traceCtxRegExp = regexp.MustCompile("^([0-9a-f]{2})-([a-f0-9]{32})-([a-f0-9]{16})-([a-f0-9]{2})(?:-.*)?$")
 
 // DefaultHTTPPropagator returns the default trace HTTP propagator.
 func DefaultHTTPPropagator() propagation.HTTPPropagator {
@@ -44,6 +50,11 @@ func DefaultHTTPPropagator() propagation.HTTPPropagator {
 }
 
 func (TraceContext) Inject(ctx context.Context, supplier propagation.HTTPSupplier) {
+	tracestate := ctx.Value(tracestateKey)
+	if tracestate != nil {
+		supplier.Set(tracestateHeader, tracestate.(string))
+	}
+
 	sc := SpanFromContext(ctx).SpanContext()
 	if !sc.IsValid() {
 		return
@@ -57,6 +68,11 @@ func (TraceContext) Inject(ctx context.Context, supplier propagation.HTTPSupplie
 }
 
 func (tc TraceContext) Extract(ctx context.Context, supplier propagation.HTTPSupplier) context.Context {
+	state := supplier.Get(tracestateHeader)
+	if state != "" {
+		ctx = context.WithValue(ctx, tracestateKey, state)
+	}
+
 	sc := tc.extract(supplier)
 	if !sc.IsValid() {
 		return ctx
@@ -70,20 +86,20 @@ func (TraceContext) extract(supplier propagation.HTTPSupplier) core.SpanContext
 		return core.EmptySpanContext()
 	}
 
-	h = strings.Trim(h, "-")
-	if !traceCtxRegExp.MatchString(h) {
+	matches := traceCtxRegExp.FindStringSubmatch(h)
+
+	if len(matches) == 0 {
 		return core.EmptySpanContext()
 	}
 
-	sections := strings.Split(h, "-")
-	if len(sections) < 4 {
+	if len(matches) < 5 { // four subgroups plus the overall match
 		return core.EmptySpanContext()
 	}
 
-	if len(sections[0]) != 2 {
+	if len(matches[1]) != 2 {
 		return core.EmptySpanContext()
 	}
-	ver, err := hex.DecodeString(sections[0])
+	ver, err := hex.DecodeString(matches[1])
 	if err != nil {
 		return core.EmptySpanContext()
 	}
@@ -92,33 +108,33 @@ func (TraceContext) extract(supplier propagation.HTTPSupplier) core.SpanContext
 		return core.EmptySpanContext()
 	}
 
-	if version == 0 && len(sections) != 4 {
+	if version == 0 && len(matches) != 5 { // four subgroups plus the overall match
 		return core.EmptySpanContext()
 	}
 
-	if len(sections[1]) != 32 {
+	if len(matches[2]) != 32 {
 		return core.EmptySpanContext()
 	}
 
 	var sc core.SpanContext
 
-	sc.TraceID, err = core.TraceIDFromHex(sections[1][:32])
+	sc.TraceID, err = core.TraceIDFromHex(matches[2][:32])
 	if err != nil {
 		return core.EmptySpanContext()
 	}
 
-	if len(sections[2]) != 16 {
+	if len(matches[3]) != 16 {
 		return core.EmptySpanContext()
 	}
-	sc.SpanID, err = core.SpanIDFromHex(sections[2])
+	sc.SpanID, err = core.SpanIDFromHex(matches[3])
 	if err != nil {
 		return core.EmptySpanContext()
 	}
 
-	if len(sections[3]) != 2 {
+	if len(matches[4]) != 2 {
 		return core.EmptySpanContext()
 	}
-	opts, err := hex.DecodeString(sections[3])
+	opts, err := hex.DecodeString(matches[4])
 	if err != nil || len(opts) < 1 || (version == 0 && opts[0] > 2) {
 		return core.EmptySpanContext()
 	}
@@ -132,5 +148,5 @@ func (TraceContext) extract(supplier propagation.HTTPSupplier) core.SpanContext
 }
 
 func (TraceContext) GetAllKeys() []string {
-	return []string{traceparentHeader}
+	return []string{traceparentHeader, tracestateHeader}
 }